Fine-grained steel hardened article



Patented Aug. 14,- 1945 1 j uurrso STAT-ES PATENT cmcc FINE-GRAINED STEEL HARDENED ARTICLE Walter Crafts, Niagara Falls, N. Y., assignorto EIec'tro Metallurgical Company, a corporation of West Virginia No Drawing. Original application March 11, 1941, Serial No. 382,737. Divided and this application'January 12, 1945, Serial No. 572,583

2 Claims. (Cl. 75-123) This invention relates to steels, and more specifically to steels the hardness of which may be iricreased by rapid cooling from temperatures within or above the critical range. For the sake of simplicity of presentation, the application of the invention will be described herein principally as it may be applied to carbon steels containing 0.1% to 1% carbon, up to about 2% manganese, and between 0.25% and 2% silicon; but as the description proceeds it will be evident that the invention may be applied to a wide variety of hardenable steels. This application is a division of my co pending application Ser. No. 382,737, filed March When hardening steels by rapid cooling from high temperatures, it is often desired toproduce a deep or thick zone of hardened material rather than a thin or shallow hardenedcase. The depth to which a piece of steel will harden, at a given rate of heat extraction, is different in different steels. The property of the steel which involves this relative susceptibility to mass effect in hardening seems to be inherent, and for convenience it will be termed herein deep-hardenability.

An accepted, convenient measure of deep-hardenability is afforded by the Jominy" test, described in detail in A Hardenability Test for Carburizing Steel by W. E. Jominy and A. L.- Boegehold, Trans. Am. Soc. for Metals, vol. 26,- p. 574 (1938). To summarize briefly, the test is made on a small bar of steel of'standardized shape and dimensions, and comprises heating the entire bar to thedesired hardening temperature, quickly extracting heat through one end face of the bar,

grinding ofl" superficial scale .and decarbnrized skin and producing a flat surface suitable for required to impart a useful degree of deep-hard- Y enability, and in the maximum degree of deephardenability obtainable while maintaining other necessary properties of the steel.

I have found that beryllium may be used to impart an even further enhanced deep-hardenability to steelscontainingbetween 0.25% and 2% silicon, without substantially sacrificing other desirable properties of the steels. I have further observed that combination of beryllium with one ormore of the further elements: the alkali metals, alkalineearth metals, aluminum, titanium, zirconium, uranium, cerium, thorium, vanadium, columbium, and tantalum, in percentages greater than those required for-grainrefinement, considerably enhances the cited; of beryllium on deep- A hardenability.

The present invention provides a fine-grained quench-hardened beryllium steel article in which beryllium is present in a percentage at least 0.0025% but less than 0.05%, and preferably between a ut 0.01% and 0.05%. The silicon content is between 0.25% and 2% and preferably be- "tween 0.35% and 1%. The carbon content is between 0.1 and 1%; and preferably between 0.2% and 0.8%. The minimum total proportion of said further element or elements to be added is any proportion greater than that required for grainreflnement, and preferably up to several times.

that required for grain-refinement. The percentage required for optimum grain-refinement making a hardness test, and measuring the Rockwell C hardness along the length of the bar. As a means for readily expressing the relation between the hardness and distance from the hardwilldepend to some extent on the kind of steel, thewsteel-making conditions, and the kind and number of deoxidizing and grain-refining elements used: but the total aggregate percentage of such further elements to be added will be between 0.03% and 1%, and a preferred range is between 0.05% and 0.3%. The steel'article of the present ened end, the distance from the hardened end at ten, chromiumQor nickel. These hardening elements differ widely in the minimum percentage hardenability and a frequent result of an increase invention also contains at least one element of the group consisting of molybdenum, tungsten and chromium, the aggregate percentage of such additional element or elements together with-the silicon percentage being at least 0.3% but less than 5% of the steel.

In good steelmaking practice an addition of beryllium amounting to between 0.01% and 0.2% will yield residualberyllium in the final steel within the percentage limits specified above.

For each element and each combination of elements there appears to be an optimum percentage which imparts a maximum depth of in percentage beyond the optimum is a decrease of deep-hardenability below that imparted by the optimum, but for reasons of economy, or to obtain a steel having a certain desired combination of physical properties. it will often be desired to add either less or more of the elements than will impart a maximum depth of hardening.

The eincacy of addition of beryllium in increasing the hardenability of steels of diflerent silicon contents may be appreciated from an inspection of the figures, derived from test data, in the table, which indicate the relative J ominy hardenability depths, in hundredths of an inch, of steels containing about .5 carbon, 1 70% manganese, the indicated added percentages of other elements, and the remainder iron.

Composition, remainder iron Steel J ominy N 0. depth C Si Mn Al V 1 Zr, Be

Per Per Per Per Per Per Per cent cent cent cent cent cc'nl cent Inch 1 0. 44 0.27 1. 0G 0. 04 0. 04 0. 04 None 0.21 l 0. 43 0. 29 1. 74 0. 04 0. 04 0. 02 0. 022 0.33 0. 50 0. 53 l. 75 O. 07 0. 07 0. 07 None 0. 56 4. 0. 52 0 49 1. 65 0. 09 0. 08 0. 04 0. 044 0. 67 5.; 0. 49 1. 0 l. 67 0. l4 0. 14 0. 14 None 0. 52 6 0,48 1.0 l. 73 0. 17 0.15 0.16 0.015 0.63 7 0. 51 1.0 l. 65 0.18 0.18 0. 00 0.088 0. 74

1 Percentage added, all other erccntages determined by analysis. Residual beryllium between 203., and 35% of percentage added.

Each of the steels in the table contains a total proportion of the elements aluminum, vanadium, and zirconium above that required for grainrefinement. It will be observed that for a given silicon content those steels which contain a proportion of beryllium within the limits prescribed in this invention exhibit a. marked increase in hardenability over steels containing no beryllium but of otherwise similar composition. In order to exhibit the remarkable eificacy of beryllium additions even at the lower end of the specifled range, a 1% silicon steel (steel No. 6) was treated with an addition of only 0.015% beryllium. In this steel the hardenability was greatly lium addition as is evidenced by the data on steel No. 7.

The efllcaoy of beryllium additions in increasing hardenability is by no means limited to steels of the particular compositions shown in the table. These steels were selected only to demonstrate the practical application of the invention which is equally applicable to a. wide variety of hardenhaving substantially the composition: 0.25% to enhanced oven a steel of similar composition 2% silicon, manganese in a substantial proportion up to 2%; 0.1% to 1% carbon; between and 0.05% beryllium, 0.03% to 1% in the aggregate of at least one deoxidizing grainrefining element; and at least one element of the group consisting of molybdenum, tungsten, and chromium, the aggregate percentage of such last mentioned element or elements together with the percentage of silicon being at least 0.3% butless than 5% of the steel.

2. A fine-grained steel quench-hardened article, other than a nitride case-hardened article, having substantially the composition: 0.35% to 1% silicon, manganese in a substantial proportion up to 2%;.0.2% to 0.8% carbon; between 0.01% and 0.05% 0.05% to 0.3% in the aggregate of at least one deoxidizing grainrefining element; and at least one element of the group consisting of molybdenum, tungsten, and chromium, the aggregate percentage of such last mentioned element or elements together with the percentage of silicon being at least 0.3% but less than 5% of the steel.

WALTER CRAFTS. 

